3 research outputs found
Palladium NâHeterocyclic Carbene Precatalyst Site Isolated in the Core of a Star Polymer
An
approach for supporting a PdâNHC complex on a soluble
star polymer with nanoscale dimensions is described. The resulting
star polymer catalyst exhibits excellent activity in cross-coupling
reactions, is stable in air and moisture, and is easily recoverable
and recyclable. These properties are distinct and unattainable with
the small-molecule version of the same catalyst
Distal Hydrophobic Loop Modulates the Copper Active Site and Reaction of AA13 Polysaccharide Monooxygenases
Polysaccharide
monooxygenases (PMOs) use a type-2 copper
center
to activate O2 for the selective hydroxylation of one of
the two CâH bonds of glycosidic linkages. Our electron paramagnetic
resonance (EPR) analysis and molecular dynamics (MD) simulations suggest
the unprecedented dynamic roles of the loop containing the residue
G89 (G89 loop) on the active site structure and reaction cycle of
starch-active PMOs (AA13 PMOs). In the Cu(II) state, the G89 loop
could switch between an âopenâ and âclosedâ
conformation, which is associated with the binding and dissociation
of an aqueous ligand in the distal site, respectively. The conformation
of the G89 loop influences the positioning of the copper center on
the preferred substrate of AA13 PMOs. The dissociation of the distal
ligand results in the bending of the T-shaped core of the Cu(II) active
site, which could help facilitate its reduction to the active Cu(I)
state. In the Cu(I) state, the G89 loop is in the âclosedâ
conformation with a confined copper center, which could allow for
efficient O2 binding. In addition, the G89 loop remains
in the âclosedâ conformation in the Cu(II)-superoxo
intermediate, which could prevent off-pathway superoxide release via
exchange with the distal aqueous ligand. Finally, at the end of the
reaction cycle, aqueous ligand binding to the distal site could switch
the G89 loop to the âopenâ conformation and facilitate
product release
Distal Hydrophobic Loop Modulates the Copper Active Site and Reaction of AA13 Polysaccharide Monooxygenases
Polysaccharide
monooxygenases (PMOs) use a type-2 copper
center
to activate O2 for the selective hydroxylation of one of
the two CâH bonds of glycosidic linkages. Our electron paramagnetic
resonance (EPR) analysis and molecular dynamics (MD) simulations suggest
the unprecedented dynamic roles of the loop containing the residue
G89 (G89 loop) on the active site structure and reaction cycle of
starch-active PMOs (AA13 PMOs). In the Cu(II) state, the G89 loop
could switch between an âopenâ and âclosedâ
conformation, which is associated with the binding and dissociation
of an aqueous ligand in the distal site, respectively. The conformation
of the G89 loop influences the positioning of the copper center on
the preferred substrate of AA13 PMOs. The dissociation of the distal
ligand results in the bending of the T-shaped core of the Cu(II) active
site, which could help facilitate its reduction to the active Cu(I)
state. In the Cu(I) state, the G89 loop is in the âclosedâ
conformation with a confined copper center, which could allow for
efficient O2 binding. In addition, the G89 loop remains
in the âclosedâ conformation in the Cu(II)-superoxo
intermediate, which could prevent off-pathway superoxide release via
exchange with the distal aqueous ligand. Finally, at the end of the
reaction cycle, aqueous ligand binding to the distal site could switch
the G89 loop to the âopenâ conformation and facilitate
product release